One of the challenges in nanofabrication is the integration of self-assembling materials into existing manufacturing strategies to achieve molecular-level process control and the ability to produce useful architectures. Films of block copolymers can be directed to assemble on chemically patterned substrates into predictable and desirable morphologies and orientations with respect to the substrate, which can be used to augment and enhance the lithographic process.
When comparing the pattern in resist to the pattern of domains induced to assemble in the block copolymer film, directed assembly has been demonstrated to achieve high degrees of pattern perfection, placement of features at the precision of the lithographic tool used to make the chemical pattern, improved dimensional control of features, improved line edge and line width roughness, and resolution enhancement by factors of two to four.
In addition, this approach is the only method that has been demonstrated to robustly achieve non-regular device-oriented geometries used in the fabrication of integrated circuits or servo patterns on hard drives, most recently with resolution enhancement by multiplication of feature density by interpolation on low duty cycle chemical patterns.
While replication of periodic structures can be easily demonstrated through graphoepitaxy of simple di-block copolymers, the insertion point of these materials in the production of integrated circuits requires the ability to replicate non-regular structures, such as long lines, short segments, sharp 90° bends, jogs, T-junctions, periodic arrays of contact openings, and combinations thereof. Casting di-block copolymers alone on such patterned substrates resulted in the formation of various defects due to the incommensurability between the inherent period of the block copolymer and the different periods abundant in non-regular structures.
To overcome this limitation, blends of diblock copolymers and homopolymers were employed (Liu, G. L.; Thomas, C. S.; Craig, G. S. W.; Nealey, P. F., Adv. Funct. Mater. 2010, 20, 1251-1257). The presence of the homo-polymer enables the system to alleviate local frustrations by distributing the homo-polymer chains non-uniformly throughout the film, segregating them to the built-in “defect” points in the structure. However, this approach was found to be limited, requiring each pattern to have a specific blend composition, requiring the fine-tuning of the composition of the ternary blend. Furthermore, this approach is limited by the low diffusion rates of the homo-polymers, hindering the homo-polymers from reaching the respective locations in the film. Thus, for various patterns, the ternary blend may reproduce the structure with poor fidelity.
In order to overcome the limitations of conventional polymer materials, the inventors of the present application found that incorporation of a supramolecular block into a conventional block co-polymer provides that additional structural flexibility needed for replicating non-regular structures with high conformity and limited number of defects.